The technique of radioimmunoassay for oxytocin has been developed. The method has been used in order to measure oxytocin level in human plasma in physiological and many pathological conditions during labor, parturition, lactation, during saline abortion and during threatened abortion. Study of the secretion of oxytocin in normal and abnormal labor by correlation with direct measurements of uterine contractility. The half life of endogenous oxytocin will be carried out. The method will be extended to measure oxytocin level from pituitary and plasma from the experimental animals particularly rats, cows and dogs during pregnancy, labor and lactation. BIBLIOGRAPHIC REFERENCES: Kumaresan, P., Han, G.S., Anandarangam, P. B. and Vasicka, A. Oxytocin in Maternal and Fetal Blood. Obstet. Gynec. 46:272, 1975. Kumaresan, P., Vasicka, A., Shah Hosseini, R., Kumaresan, M. Human plasma oxytocin surge in saline and prostaglandin abortion. Program of the Fifty-eighth Annual Meeting of the Endocrine Society (1976).